Combine the ingredients for the kala chana and set aside
Whisk the yoghurt ingredients until combined and smooth
Dice your boiled potatoes
Heat a little oil in a pan and add in your potatoes, the garlic, and salt, sauteeing on medium heat until the potatoes start to develop bronzey bits.
Add the chili powder and cumin powder, cook for another half a minute and take off the heat.
Layering: Build a base with your sweetened yoghurt, then carefully spoon the kalay chanay on top, followed by the potatoes, the tomatoes, the onions and then cilantro and chilies.
Scatter chaat masala over and an additional drizzle of tamarind chutney. Add papri or sev right before serving, but know it is delightful without!
Notes
Make ahead: the potatoes do lose their crunch as they sit, but not their flavour so if making ahead works for you then go for it!
The tamarind chutney I use is this recipe. For that recipe or any tangy spicy one you don't need to add anything, but most storebought chutneys are sweet and require a little help here
How much yoghurt you use will depend on your dish. Mine is narrow, but for a larger surface dollop the the yoghurt on the outside first and then place the chana chaat fixings in the middle.
For a more traditional kala chana chaat make the following adjustments: omit yoghurt, don't sauté the potatoes (or skip them!), double the imli chutney